This invention relates to a thermal energy utilization and conservation apparatus for use on a conventional window sash where such window sash is oriented to receive solar radiation.
Fuel economy in heating enclosed spaces, energy conservation and reduction in heating system installation costs are more desirable today than ever before when considered in relation to fuel shortages, high fuel costs and national policy. Prior to construction, buildings can be designed and located at a site to advantageously use topography, sun positions, prevailing winds, adjacent buildings, natural shading, material color and texture, etc., in order to reduce heating requirements. Economics and availability of fuel supplies can be factored into selection of the thermal control system.
However, for the majority of heated structures, whether residential, commercial or industrial, which are already constricted and in use, significant reduction in consumption of thermal energy is only accomplished by reduction in usage of the facility or its heat generating equipment or by relatively significant and costly modification to the structure to reduce heating requirements.
Venetian blinds have been used in the past to control entrance to an enclosure of light and thermal energy by using a highly heat-absorptive coating on one face of the blind slats and a reflective surface on the other face. Blinds of this type are described in U.S. Pat. Nos. 2,288,465, 2,857,634 and 3,012,294. However, conventional blinds have been inefficient and ineffective in delivering solar heat to a room because a blind having its slats in the "closed" position to block direct sunlight (and prevent fading of curtains, carpets, furniture, etc.) transfers heat to the room only from the slat surfaces facing into the room. This occurs by natural convection of room air over the inner surface which, unfavorably from the standpoint of heat transfer, has a temperature not insubstantially cooler than the outside surface directly receiving radiant energy. Little, if any, energy passes directly to the room air from the hotter outer slat surfaces because present venetian blind construction and installation traps air and prevents free circulation in the space between window pane and slat surfaces.
Thus, desirable features in the construction of a blind apparatus using solar energy to supplement room heating are efficient performance, simplicity, ease of installation, low initial cost, attractive appearance and minimal, if any, power consumption in operation.